10 定义的章节样式，如何将某些节点可动态根据上一个节点的大小，来适当调整上下的位置？

只需以 description 节点为基点做平移即可

\documentclass{book}

\usepackage[explicit]{titlesec}

\usepackage[margin = 2cm]{geometry}
\usepackage{enumitem}
\usepackage{tikz}


\usepackage{graphbox} % provide align = c 

\makeatletter
\def\@chapter@description{}
\def\@chapter@objectives{}
\titleformat{name = \chapter}{}{}{0em}
{%
  \begin{tikzpicture}[remember picture, overlay, every node/.style={inner sep = 0pt, outer sep = 0pt}]
    \node[anchor = north west] at ([shift = {(2cm, -2cm)}]current page.north west) {\includegraphics[width = .2\textwidth, height = \textheight]{example-image}};
    \fill[gray!40] ([shift = {(2cm + .2\textwidth, -2.5cm)}]current page.north west) rectangle ++ (.8\textwidth, -4cm);
    \node[anchor = south west, inner sep = 10pt, scale = 2, font = \bfseries] at ([shift = {(2cm + .2\textwidth, -6.5cm)}]current page.north west) {#1};
    \fill[gray!70] ([shift = {(-2, -2.5)}]current page.north east) rectangle ++ (-1.5, -4);
    \node[rotate = 90, font=\bfseries\Large]  at ([shift = {(-2.75, -4.5)}]current page.north east) {\chaptername\ \thechapter};
    \node[anchor = north west, inner sep = 10pt] (description) at ([shift = {(2cm + .2\textwidth, -6.5cm)}]current page.north west) {
      \begin{minipage}{\dimexpr .8\textwidth - 10pt\relax}
        \parindent=2em
        \@chapter@description
      \end{minipage}
    };
    \fill[shading=radial, left color=startcolor, right color=stopcolor] ([shift = {(1, -.5cm)}]description.south west) rectangle ++ (.7\textwidth, -0.8cm);
    \node[anchor = west, inner sep = 10pt, scale = 1, font = \bfseries] at ([shift = {(1, -.9cm)}]description.south west) {Objectives};
    \node[anchor = north west, inner sep = 10pt] at ([shift = {(1, -1.9cm)}]description.south west) {
      \begin{minipage}{\dimexpr .8\textwidth - 10pt\relax}
        \parindent=2em
        \@chapter@objectives
      \end{minipage}
    };
  \end{tikzpicture}
}
\newcommand{\icon}[1]{\includegraphics[height=1em, align = c]{#1}}
\NewDocumentEnvironment{fancychapter}{m+m+b}{%
  \def\@chapter@objectives{#3}
  \def\@chapter@description{#2}
  \chapter{#1}
  \newpage
}{}
\makeatother

\usetikzlibrary{calc, intersections}
\begin{document}
\setlist[itemize]{noitemsep, leftmargin=*, label=}
% 定义渐变色
\definecolor{startcolor}{RGB}{128,128,128} % 起始颜色为黑色
\definecolor{stopcolor}{RGB}{245,245,245} % 结束颜色为白色
\begin{fancychapter}{Introduction \LaTeX}{
    The principles of object-oriented programming, such asmodularity and reusability, are quite popular as they helpin reducing the complexity of programs. In order toimplement such principles in real world applications, suchas library management and nventory management, youneed to make use of an object-oriented language, such asJava.

    This chapter focuses on the fundamentals and buildingblocks of the Java programming language. In addition, itexplains how to access the class members.

    The principles of object-oriented programming, such asmodularity and reusability, are quite popular as they helpin reducing the complexity of programs. In order toimplement such principles in real world applications, suchas library management and nventory management, youneed to make use of an object-oriented language, such asJava.

    This chapter focuses on the fundamentals and buildingblocks of the Java programming language. In addition, itexplains how to access the class members.
    
    The principles of object-oriented programming, such asmodularity and reusability, are quite popular as they helpin reducing the complexity of programs. In order toimplement such principles in real world applications, suchas library management and nventory management, youneed to make use of an object-oriented language, such asJava.

    This chapter focuses on the fundamentals and buildingblocks of the Java programming language. In addition, itexplains how to access the class members.
}
{
  \begin{itemize}
  \item \icon{example-image} Some test text.
  \item \icon{example-image} Some test text.
  \item \icon{example-image} Some test text.
  \item\icon{example-image}  Some test text.
\end{itemize}
}
\end{fancychapter}



\end{document}